In the past 2 years, significant advances have been made in class III
antiarrhythmic drug therapy. In patients with ventricular arrhythmias and
implantable cardioverter defibrillators (ICDs), antiarrhythmic agents are increasingly being used as adjunct
therapy to decrease the frequency of ICD discharges.
Sotalol was recently shown to be effective in reducing
tachyarrhythmias in patients with ICDs. Intravenous
amiodarone is being used for the acute treatment of unstable ventricular
arrhythmia and is being investigated for the treatment of acute
out-of-hospital cardiac arrest. Class III agents are increasingly being used for prophylaxis in patients who have
atrial fibrillation or
atrial flutter, and data point to an important role for these agents in reducing supraventricular
tachyarrhythmias after cardiac surgery. Future studies will need to directly compare these agents with pure anti-
adrenergic maneuvers in postoperative patients. In addition to terminating
atrial fibrillation and
atrial flutter,
ibutilide significantly reduces human atrial defibrillation thresholds and increases the percentage of patients who can be cardioverted from
atrial fibrillation to sinus rhythm. The US Food and Drug Administration is expected to approve
dofetilide for clinical use soon, and it is currently reviewing
azimilide (which seems to be devoid of frequency-dependent effects on repolarization) for prophylaxis against
atrial fibrillation and
atrial flutter.
Dronedarone, tedisamal, and
trecetilide are now under active study intended to determine their usefulness in patients with
cardiac arrhythmias. Experimental studies are ongoing to identify pharmacologic agents that will selectively prolong repolarization in the atria without exerting electrophysiologic effects in the ventricles.